I started exploring radical feminism online about two years ago, and since then I've identified as a radfem, although I don't claim to be an expert on it. I was just mightily relieved to find women who were articulating problems I'd long had with mainstream liberal feminism and was blown away by the intellectual depth of their investigations into the roots of patriarchy. I agree with LRD that radical feminism is a coherent theory, whereas IMO other feminisms (such as liberal and Marxist) fail to properly account for the ancient and worldwide oppression of women by men.
1) What does radical feminism mean to you?
Radical comes from the Latin 'radix', meaning root, and radical feminist theory is an attempt to identify the root of women's oppression, while radical feminist practice attempts to dismantle the material and ideological institutions that support it. That means that no aspect of society or human relations is off limits to radical critique.
Radical feminism, in my understanding, locates this root in the male colonisation of female sexuality and reproductive capacity. Because women can bear children and men cannot, men will always try to control us. In almost all known human societies, members of the female sex caste are treated differently from birth, forced into an inferior social role, exploited for their domestic labour, subjected to male violence and then blamed for it, and sexually objectified. This is all naturalised by a system called 'gender'.
2) What aspects of feminist theory would you attribute to radical feminism?
Radical feminists produced almost all of the theory of the second wave: the dissection of gender roles as unnatural and part of the structure of women's oppression; the exploitation of women's unpaid domestic and affective labour as a central pillar of capitalism; male eroticisation of women's subordination; rape as a tool of patriarchal control, not a product of sex mania; the exploitation and control of women's reproductive capacities as the material basis of the sex-caste system; the fact that this system actually predates and underlies later exploitative social strata like economic class.
As others have noted, the most important of these theories is the identification of male violence as the core strategy of political control of women as a class. As I understand it, liberal feminists of the time were actually embarrassed by the radfem focus on rape and violence - they preferred to concentrate on issues like equal pay and political representation, not realising that women's social and economic inferiority was intimately related to the eroticisation of violence against us, the impunity afforded to men who committed it, and the material effects of this.
All feminists now recognise male violence as a central issue, but liberal feminists IMO have watered down the analysis to obscure the understanding of it as a deliberate strategy of political control. They proceed as if it is all a mistake that men need to be educated out of. For instance, they believe that men rape because they haven't been sufficiently educated about consent. They don't say 'male violence against women', they say 'gender-based violence', which hides the agent. In so doing, they prevent women from getting to the root of the problem.
3) What makes someone a radical feminist?
A commitment to getting to the root of women's oppression, which means being prepared to follow your thoughts and the thoughts of other women to their conclusions, instead of stopping half way when those conclusions become uncomfortable. Most of all, radical feminism involves an unqualified commitment to putting the interests of women and girls first.
4) What makes radical feminism different from other strands of feminism?
Catherine MacKinnon has described radical feminism as feminism unmodified, and I agree with that. This means that if something works against women's interests, it should never be defended on any grounds, despite whatever male theory (liberalism, neoliberalism, cultural relativism, etc.) is deployed to justify it.
I put women and girls first, not because I'm indifferent to the injustices faced by boys and men, but because someone has to. I would like to reshape the world in the interests of the freedom and full humanity of women and girls, and this means that most social, economic and cultural institutions need to be radically re-imagined or abolished. This is deeply uncomfortable for many women, and outright resisted by men.